/*
 *
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */

package org.apache.paimon.mergetree.compact.aggregate;

import org.apache.paimon.types.DataType;

/** first value aggregate a field of a row. */
public class FieldFirstValueAgg extends FieldAggregator {

    public static final String NAME = "first_value";

    private static final long serialVersionUID = 1L;

    private boolean initialized;

    public FieldFirstValueAgg(DataType dataType) {
        super(dataType);
    }

    @Override
    public String name() {
        return NAME;
    }

    @Override
    public Object agg(Object accumulator, Object inputField) {
        if (!initialized) {
            initialized = true;
            return inputField;
        } else {
            return accumulator;
        }
    }

    @Override
    public void reset() {
        this.initialized = false;
    }
}
